When a user is interacting with a computer, there are three main areas of
contextual information that may affect the behaviour of the system: who the user
is, where they are, and what they are doing.

Activities deal with the last one. An activity might be "developing a KDE
application", "studying 19th century art", "composing music" or "watching funny
videos". Each of these activites may involve multiple applications, and a single
application may be used in multiple activities (for example, most activities are
likely to involve using a web browser, but different activities will probably
involve different websites).

KActivities provides the infrastructure needed to manage a user's activites,
allowing them to switch between tasks, and for applications to update their
state to match the user's current activity. This includes a daemon, a library
for interacting with that daemon, and plugins for integration with other
frameworks.
